fix: Reader should be drainable after writer disconnects

Fix an issue where dropping the writer while some data still remained in the pipe caused the reader to return an error instead of allowing you to drain the bytes in the pipe until empty.

src/pipe/chunked.rs

@@ -117,7 +117,17 @@ impl AsyncRead for Reader {
                     // of buffers, so this can never happen.
                     if e.is_full() {
                         panic!("buffer pool overflow")
-                    } else {
+                    }
+
+                    // If the writer disconnects, then we'll just discard this
+                    // buffer and any subsequent buffers until we've read
+                    // everything still in the pipe.
+                    else if e.is_disconnected() {
+                        // Nothing!
+                    }
+
+                    // Some other error occurred.
+                    else {
                         return Poll::Ready(Err(io::ErrorKind::BrokenPipe.into()));
                     }
                 }
@@ -193,6 +203,23 @@ mod tests {
             let mut dest = [0; 5];
             assert_eq!(reader.read(&mut dest).await.unwrap(), 5);
             assert_eq!(&dest, b"hello");
-        });
+        })
+    }
+
+    #[test]
+    fn reader_still_drainable_after_writer_disconnects() {
+        block_on(async {
+            let (mut reader, mut writer) = new(1);
+
+            writer.write_all(b"hello").await.unwrap();
+
+            drop(writer);
+
+            let mut dest = [0; 5];
+            assert_eq!(reader.read(&mut dest).await.unwrap(), 5);
+            assert_eq!(&dest, b"hello");
+
+            assert_eq!(reader.read(&mut dest).await.unwrap(), 0);
+        })
     }
 }